How long do you need probiotics for them to take effect?

In past decades, nobody would have guessed that eating bacteria would be anything but dangerous. When they were first discovered as the source of many diseases, bacteria were automatically tagged as harmful, and many people maintain the same notion, especially if they don’t know much about probiotics.

We can find healthy bacteria in the skin and mucosa of the entire body, and they do not harm us in any way. Healthy bacteria are often known as microbiota, and there’s a distinct microbiota in the gut, the oral cavity, the urethra, the vagina, and other body parts in direct contact with the outside.

Healthy bacteria protect us against pathogenic bacteria. They compete for a place in the gut, and do not allow bad microbe colonization. For that purpose, we need a constant influx of good bacteria to maintain a proper balance and prevent gastrointestinal disease. However, how much time do we need to use probiotics to start seeing the benefit? The answer to that question depends on our state of health and our goals and motivations to use probiotics in the first place.

Why do probiotics take time to produce an effect?

Probiotics rarely act instantaneously. So, you will definitely need some time consuming them to start seeing benefits. It’s not similar to an anti-inflammatory pill you take to relieve a headache or the antacids your chew in the case of a heartburn. Some of these pills are very hard and go through the stomach without any change.

Probiotics are different. They are living bacteria, and the processing to deliver them to the gastrointestinal tract is not the same. They actually need some moisture to remain alive, and the best you can do if you want them in a pill form is using soft-gel capsules. Ideally, you should maintain them in a liquid form. But either way, they need to go through the stomach, and the acid environment is not bacteria-friendly.

In the end, you get a reduced number of bacteria, and it is very difficult to say exactly the ratio that survives the journey in your particular case. Moreover, even if a considerable proportion reaches the intestines, it takes a while for them to settle in place, start their metabolic processes, and actually make a difference. Thus, you need to keep consuming this type of food or supplements for them to take effect.

Probiotics on the short-term and the long-term

You don’t get an instantaneous relief with probiotics, but that doesn’t mean they won’t make a difference in a day or two. Short-term effects of probiotics are mainly experienced by people who have severe gastrointestinal problems, and they usually take at least 1 or 2 days. In these days, you should be consuming the recommended dose, and severe cases may require a higher dosage to maximize the effects in a short time. For example, many patients with diarrhea have found significant improvements after 1 to 3 days of probiotics use in the higher dose.

This short-term effect does not take a lot of time because it only requires the presence of the bacteria in the gut, and nothing more. The number of healthy bacteria increases, they start replicating, and compete with pathogenic bacteria, washing them away from the intestines. They do not need complex metabolic processes and other conditions to do that.

On the other hand, there are also long-term effects of probiotics that may take weeks or months to take place. For example, boosting your immunity or using probiotics to strengthen the brain-gut axis may take a very long time, usually a few weeks and sometimes a few months.

According to clinical trials, an extended long-term use of probiotics can be used to prevent gastrointestinal disease, especially when they have to do with avoiding the harm of pathogenic bacteria or keeping the inflammation of the gastrointestinal system in check. For example, using probiotics for 9 months and more is accepted as an effective method to prevent pouchitis, an inflammatory disorder with unknown causes that responds to probiotic treatment after long-term use.

If we take a look at clinical trials, most of them use probiotics for 8 weeks, which is almost two months. This is enough time to populate the gut with healthy bacteria, and enough time to allow their metabolic machinery to fully activate.

So what is the Conclusion?

Probiotics almost never act instantaneously. They always need some time to reach the gastrointestinal tract, populate the gut, and start their metabolic processes. However, we do have short-term and long-term effects of probiotics.

On the short-term, probiotics can act in 1-3 days by reducing diarrhea and other alarming gastrointestinal symptoms, especially in the event of a pathogenic bacteria. On the long-term, probiotics may take a few weeks and even months to produce their effects, especially if you’re planning to use them as a part of your prevention strategy.

What we recommend if you’re considering probiotics for the first time is to start with a high dose for one or two days, especially if you have very annoying gastrointestinal symptoms. Reduce your dose to the standard when your symptoms are mild, and to the minimum when you don’t have any symptoms at all.

Repeated use of probiotics when you’re not sick is recommended, and it is a good way to prevent inflammatory disease in in the gastrointestinal tract. If you want to use probiotics this way, do not forget your daily supplement. The only way to replicate the effects reported by clinical trials is by not forgetting to take them every day for a given period of time.


Tomasz, B., Zoran, S., Jarosław, W., Ryszard, M., Marcin, G., Robert, B., … & Przemysław, P. (2014). Long-term use of probiotics Lactobacillus and Bifidobacterium has a prophylactic effect on the occurrence and severity of pouchitis: a randomized prospective study. BioMed research international, 2014.

Hempel, S., Newberry, S., Ruelaz, A., Wang, Z., Miles, J. N., Suttorp, M. J., … & Smith, A. (2011). Safety of probiotics used to reduce risk and prevent or treat disease. Evidence report/technology assessment, (200), 1.

Khan, S., & Chousalkar, K. K. (2020). Short-term feeding of probiotics and synbiotics modulates caecal microbiota during Salmonella Typhimurium infection but does not reduce shedding and invasion in chickens. Applied Microbiology and Biotechnology, 104(1), 319-334.

Gao, R., Zhang, X., Huang, L., Shen, R., & Qin, H. (2019). Gut microbiota alteration after long-term consumption of probiotics in the elderly. Probiotics and antimicrobial proteins, 11(2), 655-666.

About Simon Bendini 78 Articles
Hello, I'm an expert in all things Probiotics. I also live and breathe what I write about: I take Probioitcs EVERY day. I want to help you discover the benefits of them too. Enjoy my humble site.

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